CERVICAL VERTEBRAE OF HESPERORNIS. 27 



Vertical diameters of posterior articulation of centrum, 8.0-11.0 mm 



Transverse diameter of vertebra, across pre-zygapophyses, - 20.0 



Transverse diameter of vertebra, across post-zygapophyses, 21.0 



Diameters of pre-zygapophyses, . 6.5-12.0 



Diameters of post-zygapophyses, 7.0-11.0 



Length of floor of neural canal, 31.0 



Total length of pleurapophysis, . . . 29.0 



Length of free portion of pleurapophysis, 21.0 



Measurements. (No. 1207.) 



Length of centrum, 30.0 mm 



Transverse diameters of anterior articulation of centrum, 11.5-14.0 



Vertical diameters of anterior articulation of centrum, 5.5- 9.0 



Transverse diameter of posterior articulation of centrum, 16.0 



Transverse diameter of vertebra, across pre-zygapophyses, 28.0 



Transverse diameter of vertebra, across post-zygapophyses,. 27.0 



Grsatest diameter of pre-zygapophyses, 9.0 



Least diameter of pre-zygapophyses, 5.2 



Greatest diameter of post-zygapophyses, 10.0 



Transverse diameter of anterior opening of neural canal, 10.0 



Vertical diameter of anterior opening of neural canal, . 7.0 



Length of pleurapophysis, 23.0 



Length of free portion of pleurapophysis, . . 18.0 



Diameter of free portion of pleurapophysis, at base, 5.5 



Vertical diameter of lateral foramen, . 5.8 



Transverse diameter of lateral foramen, . . 4.0 



The Seventh Vertebra. (Plate III, figure 6.) 

 The seventh vertebra is slightly longer and larger than the sixth. The 

 centrum has the lateral ridge above the groove for the vertebral artery less 

 developed than in . the sixth, and not coalescing with the ridge below ; 

 which, on the other hand, is well developed, and clearly bounds the lower 

 svu-face of the centrum. This surface is broader than in the sixth vertebra, 

 and widely excavated longitudinally, throughout, the excavation being 

 much deeper and wider anteriorly than in the sixth vertebra, and nowhere 

 disappearing on the surface of the centrum. Just behind the outer 

 inferior margin of the anterior articular face on each .side, is a tubercle, 

 somewhat elongated longitudinally with the vertebra, and projecting 

 downward, and slightly inward. These tubercles become a prominent fea- 

 ture on some of the succeeding vertebrae of the series, but only the faintest 

 trace of them is visible on the sixth vertebra, and they may be considered 



